The unique capacity of monoclonal antibodies to distinguish between cells that morphologically appear identical will be employed to gain new insight into the differentiation pathways of human connective tissue cells. Once differentiation antigens are identified and characterized they will be used as markers for the more accurate classification of human sarcomas. In the first year of the grant the focus has been on establishing the technology necessary for conducting the proposed studies. We have developed a new system for generating hybridomas producing monoclonal antibodies which is five-to-seven-fold more efficient than those using standard techniques. Also completed is the development of a new quantitative ELISA assay for the detection of monoclonal antibodies binding to the surfaces of viable tumor cells. Progress is now being made in securing monoclonal antibodies to connective tissue differentiation antigens. In the first year, a large number of monoclonal antibodies were generated following immunization of mice with human sarcomas. These have been thoroughly screened using panels of human sarcoma and carcinoma cultures as well as normal human fibroblasts. A group of these monoclonal antibodies have been identified as specific for connective tissues and they are now undergoing evaluation for their in vivo specificity. In the coming year, we will fully evaluate the monoclonal antibodies now in hand and continue to develop new monoclonal antibodies needed to permit us to fully explore the diversity of connective tissue cells.